Wheel lifting linkage for pallet trucks



' May 10, 1949.

H. J. FRAMHEIN WHEEL LIFTING LINKAGE FOR PALLET TRUCKS 2 Sheets-Sheet 1 Filed July 20, 1943 IIYVENTOR ATI'ORNEY ln sguwfir III. igllllill l 1E Patented May 10, 1949 UNITED STATES PATENT OFFICE 2,469,638 WHEEL LIFTING LINKAGE FOR PALLET TRUCKS Herbert J. Framhein, Chicago, 111., assignor to The Yale & Towne Manufacturing Company, Stamford, Conn., a corporation of Connecticut Application July 20, 1943, Serial No. 495,453

6 Claims.

This invention relates to an industrial truck of the type in which an elevating platform is adapted to lift a skid or pallet, and thereafter to transport the skid or pallet to a point where it is to be deposited. More specifically, my invention relates to a truck of the type that is disclosed in the Quayle Patent No. 2,274,164 and in my earlier applications Serial Nos. 432,177, filed February 25, 1942, now Patent No. 2,399,596, April 30, 1946; 481,957, filed April 6, 1943, now Patent No. 2,439,599, April 13, 1948; 458,035, filed September 11, 1942, now Patent No. 2,415,090, Feb. 4, 1947, and 469,324, filed December 17, 1942, now Patent No. 2,417,394, March 11, 1947.

In the truck shown in the Quayle patent and in my earlier applications, an elevating platform is adapted to be lifted at its rear end by the downward swinging movement of lifting wheel links pivoted to the elevating patform and carrying lifting wheels. Operating members, such as rods, cables, levers, or the equivalent, are employed in my earlier applications and in the Quayle patent, to pull the lifting wheel links and thereby rotate the said links on their pivots relatively to the elevating platform so as to lift the elevating platform. These members, which may be called tension members, are naturally mounted for movement under the elevating platform and are pivoted to the lifting links on which the lifting wheels are carried.

Because in these earlier structures the elevating platform is lowered almost against the ground so that it may enter between the upper and lower floors of a pallet, there is naturally very little room available for a satisfactory connection between the lifting wheel links and the tension members. In addition, the lifting Wheel links must move almost to a horizontal position when the elevating platform is fully lowered. Therefore, since the tension members are secured to the lifting links, their direction of pull is but slightly offset from the axis about which the lifting wheel links are rotatable to lift the elevating platform. Be-' cause of this relationship of the parts, the initial lifting of the elevating platform in prior art trucks or the particular class described is extremely difilcult. It may be well to indicate that the use by me of the descriptive term tension member is merely to facilitate the description of my invention. Actually, it is conceivable that the members connected to the lifting wheel links, may be other than tension members.

In those disclosures shown in my Patents 2,415,090 and 2,417,394 where the lifting wheels are held upwardly from the ground, the lowering of the lifting wheels during their first movement against the ground is facilitated because the lifting wheels are not required to lift a load during the first movement. Once the lifting wheels contact the ground, the problem of moving the lifting v 2 wheel links thereafter is the same in the structure of the said Patents 2,415,090 and 2,417,394 as it is in my Patents 2,399,596 and 2,439,599, in which the lifting wheels are not lifted off the ground.

The object of this invention is to devise means whereby downward swinging movement of the lifting wheel links may be more readily and easily efiected. As a feature of my invention whereby the said object is achieved, I utilize an intermediate link between each of the lifting wheel links and the means used for swinging the said links downwardly. More particularly, a feature of my invention resides in an intermediate link that is preferably pivotally connected to a lifting wheel link and to a tension member, whereby to transmit the movement of the tension member to the lifting wheel link.

As a further feature of my invention, the intermediate link connected to the tension member and the lifting wheel link, is guided so that the pivot between it and the tension member is vertically displaced from its pivotal connection with the lifting wheel link so that the line of tension is considerably displaced from the pivotal axis of the lifting wheel link. In this way, a more efficient operation of the lifting wheel link by the tension member is obtained.

As a still further feature of the invention, a guide means is used for guiding the intermediate link so that its pivotal connection with the tension member is considerably below its pivotal connection with the lifting wheel link, whereby to allow the application of the force of the tension member in an efiicient manner. As a further detailed feature of my invention, the guide means may take the form of a fulcrum stud in one modification of my invention, and a roller in another form of my invention, all as will be made quite apparent hereinafter.

I have thus presented generally the problem solved by my invention, as well as a broad outline of the structure of my invention, in order that the contribution of my invention to the prior art may be better appreciated. There are, of course, additional features of my invention that I have not as yet set forth, but which I shall describe in the specification and claim in the claims appended hereto. It will be well to consider that my invention is a broad and valuable one and that I am entitled to claims that will prevent the appropriation of my invention in physical forms other than the particular forms shown and described.

Referring now to the drawings,

Fig. 1 is a vertical elevation of a truck to which my invention is applied.

Fig. 2 is a view looking downwardly on one leg of the U-platform of the truck of Fig. 1.

Fig. 3 is a'section taken along lines 3-3 of 3 Fig. 2 showing the lifting wheels lifted off the ground.

Fig. 4 is a vertical View similar to Fig. 3 but showing the lifting wheels against the ground. Fig. 5 is a view showing the lifting links in their fully lifted position.

Fig. 6 is a view similar to Fig. 3 illustrating a modification of my invention and showing in phantom the parts thereof whie'i'iin a' lifting position similar to that of Fig. 5.

Referring now more particularly to the drawings and especially Fig. 1, my" invention there" is shown applied to a truck of the type illustrated in my Patent 2,415,090.- So far as the present invention is concerned, it is only necessary to know that the said truck has a'ri elevating 51stform if! and a lifting head H, and that when the elevating platform is raised, cams l2'will be rotated about pivots [3 to' move tension" bar's I'd in the direction of the arrow [5.

Trucks of the particular type are adapted to have their platforms enter between the upper and lower floors N5 of a palletP and to raise'th'e pallet when the elevating p1a'tforr'nis" lifted. Lifting movement is imparted to therearencl of the elevating platform by lifting wheels ll mounted on axles l8 carried by lifting links I191 In the truck to which my invention is" shown applied, the elevating platform ill of the U'-t'y'pe and is formed with two legs Hid, each leg I (la having a lifting link l9 on which is mounted a lifting wheel I1. In describing my invention further, I shall describe the structure of but one of the legs [a of the U-plat'foi'rn' Ill, and the lifting link' It! and the operating mechanism associated therewith.

The lifting link I!) is'piv'o'ted about shaft 20 supported by the opposed bearing blocks 2! welded as at 22 to the leg' lll'a of' the platform It (Fig. 2). In the trucks of-the prior art; and in the truck of my" earlier applications" and of the Quayle patent, it is the custom to pivot ally connect the tension bar M' directly to the lifting link 19 for swinging that link' downwardly from its position of Figs. 3 and 4 to the position of Fig. 5. If this is done, the pivotal connection must be approximately in' the axis of a shaft designated by reference numeral 23 in Figs. 3 and 4. Those skilled in the art will readily appreciate that any tension that may be brought by the tension bar 14, if secured as about pivot shaft 23 to the lifting link l9, will; be a line extremely close to the pivot shaft All aboutwhich the lifting link I9 is rotatable; Therefore) the application of lifting effort through" the tension bar I l at the beginning of the lifting stroke} is extremely inefiicient pallet truckso'f the prior art.

For obtaining greater lifting efficiency I have utilized what I term an intermediate link 25 This intermediate link 25'is'formedwi'thfah upper tubular portion 26 that is pivoted to the lifting link so through the intermediary of a shaft- 23; The intermediate link 25' is formed with a" pair of cam surfaces 28, one at each end thereof, the purpose of these cams being to guide or fulcrum the intermediate link as it transmits lifting effort from the tension bar I4 to the lifting Wheel-link [9. The tension bar |'4- is pivoted through'shaft 30'to the intermediate link-25 and throughthe said shaft 30 imparts motion to the intermediate link.

For cooperation withthecam surfaces 28 ,-I employ a pair of studs; 3-l,-one foreachof the cam surfaces 28. Each of the studs 3| is carried on the end of a stud shaft 32 that passes through a bore'in'one of the opposed bea ririg blocks 21. A nut 33 is secured on the threaded end of each of the stud shafts 32, for holding the shafts and s'tuds 3| in position.

Where=theconstruction of my Patent 2,415,090 is utilized; that is, a construction in which the lifting wheels I! are initially spaced from the grouse, the will occupy the position of Fig. 3 in the lowered position of the elevating platform l0. Should tension be applied to the tension bar [4-, the tension bar will pull on the intermediate link through the pivot shaft 3!]. The cam surfaces 28 of the intermediate link 25 bear against the studs 3! with the studs acting as fulcrums, so that the pull of the tension bar 44 Will swing the lifting" link I9 downwardly" into theposition of Fig. 4. The shape of each of the oath surfaces 28 is such that the's a id camshfaces will merely roll about the surfaces of the fulcrum studs't'l, thereby making it"unn'eces'sa'ry to use rollers in the place of the" said studs. It will of course be quite apparent that the pull of the tension bar M will be displaced considerably more from the pivot shaft 20' of thelifting link [9 than" in the prior art structures where the tension bar ['4 is secured directly to the lifting link IE3. This, togetherwith 'the lever-like action of intermediate link'25" contributes a much'nio're effifcie'iit application Of the force of tension bar M than'heretofore possible. H

If we consider the structure of Fig. l as illustrative of the type of truck shown irrthe' Quayle patent in which the lifting wheels are always against the ground; it Will be noted that there also'it is'po'ss'ible to obtain'a much more efficient application of the force of the tension bar l4 than in the prior art. With the parts'inthe position of Fig. 4, application of tension th'rou'gh'the' tension bar M will of course move the parts from the position of Fig. 4" to the final lifted positionof Fig. 5'. It is interesting to note that in th e'pos'i tion of the parts in Fig. 5, the" particular cam surface 28 of lifting link l9 that is shown, has moved away from its stud 35. It will bewell to note'that this movement of the ca'msurface's' 28 away from the studs 3|, takes place as soon as the pivot shafts '23' and are aligned with the direction of-pull of the tension bar [4.

With the parts ih'the position of Fig; 5, should the'elevating platform be lowered, the partswill of coursembve backwards to the position of Fig. 4' and thence to the position of Fig. 3 all as is quite apparent. A" block 35' extends upwardly from" the'jlin'k l9 and impinges against' a'; limit surface36 on the elevating platform t'o'limit the upwardly swinging movement of the lifting link l9.

In Fig. 6 I show a modified form of my invention in which the studs 3| are eliminated, there' being substituted therefor rollers 40 mounted for rotation" about stud'sh'afts 4| that are secured iri placeas are the shafts'32 of the first modification. Thec'a/n'i surfaces 28 of the first modificat'icn are eliminated, and instead, the intermediate; link, designated here by refer"- ence numeral 25d, is formed with a simple ca surface 42 that cooperatesiwith the rollers 40. The simple surface 42 will not roll about the rollers 40, andit is therefore necessary to; use rollers instead of the" circular studs" 3i of the first modificati' Other than" the par'ticular difie renceset f5 ateseiiactly a's'db meritorious features will now be quite apparent to those skilled in the art.

I now claim:

1. In a truck of the class described, a lifting wheel link, means rotatably mounting said link on a, part of said truck, a lifting wheel mounted on said link, tension means for pulling said link to rotate it on said mounting means in a downwardly extending arc from an upward position to a lowered position, an intermediate link pivoted to said lifting wheel link at one end and to said tension means at its other end and through which said tension means swings said lifting link downwardly, and a guide member mounted on a fixed point on said truck part for guiding said intermediate link and so located that when said lifting wheel link is in its upward position the pivot between said intermediate link and said tension means is vertically below the pivot between said intermediate link and said lifting wheel link.

2. In a truck of the class described, a lifting wheel link, means rotatably mounting said link on a part of said truck, a lifting wheel mounted on said link, tension means for pulling said link to rotate it on said mounting means in a downwardly extending are from an upward position to a lowered position, an intermediate link pivoted to said lifting wheel link at one end and to said tension means at its other end and through which said tension means swings said lifting link downwardly, and a fulcrum member mounted at a fixed point on said truck part for guiding said intermediate link and so located that when said lifting wheel link is in its upward position the pivot between said intermediate link and said tension means is vertically below the pivot between said intermediate link and said wheel link, the pull of said tension means acting to move said intermediate link about said fulcrum member whereby to rotate said lifting wheel link.

3. In a truck of the class described, a lifting wheel link, means rotatably mounting said link on a part of said truck, a lifting wheel mounted on said link, tension means for pulling said link to rotate it on said mounting means in a downwardly extending arc from an upward position to a lowered position, an intermediate link pivoted to said lifting wheel link at one end and to said tension means at its other end and through which said tension means swings said lifting link downwardly, and a guide member mounted at a fixed point on said truck part for guiding said intermediate link and 50 located that when said lifting wheel link is in its upward position the pivot between said intermediate link and said tension means is vertically below the pivot between said intermediate link and said lifting wheel link, the pull of said tension means acting to align said pivots with the direction of the pull of said tension means, whereupon said intermediate link is released from the control of said guide member.

4. In a truck of the class having a lifting head and an elevating platform mounted for lifting movement relatively to said lifting head and movable from a low position adjacent the ground to an elevated position, a lifting wheel link, means rotatably mounting said link on the underside of the rear end of said elevating platform for lifting said rear end, a lifting wheel mounted on said link, a tension member extending under the elevating platform from its forward end to said lifting wheel link for rotating said link in a down- 6 wardly extending are from an upward position whereby to lift the elevating platform, and a short intermediate link pivoted to said lifting wheel link and to said tension member with the line between the pivots substantially vertical when said lifting wheel link is in its upper position, said tension member swinging said lifting wheel link downwardly through the intermediary of said intermediate link.

5. In a truck of the class having a lifting head and an elevating platform mounted for lifting movement relatively to said lifting head and movable from a low position adjacent the ground to an elevated position, a lifting wheel link, means rotatably mounting said link on the underside of said elevating platform, a lifting wheel mounted on said link, said lifting wheel link lying with the axis of rotation of said lifting wheel thereon approaching the level of the axis of rotation of said lifting wheel link on said mounting means when said elevating platform is lowered, a tension member extending under the elevating platform from its forward end to said lifting wheel link for rotating said link in a downwardly extending arc on said mounting means whereby to lift the elevating platform, an intermediate link pivoted to said lifting wheel link and to said tension member and with the pivots substantially vertically aligned, and a fulcrum for said intermediate link against which it is urged and relatively to which it is moved by said tension member to swing said lifting wheel link downwardly.

6. In a truck of the class having a lifting head and an elevating platform mounted for lifting movement relatively to said lifting head and movable from a low position adjacent the ground to an elevated position, a lifting wheel link, means rotatably mounting said link on the under side of said elevating platform, a lifting wheel mounted on said link, said lifting wheel link lying with the axis of rotation of said lifting wheel thereon approaching the level of the aXis of rotation of said lifting wheel link on said mounting means when said elevating platform is lowered, a tension member extending under the elevating platform from its forward end to said lifting wheel link for rotating said link in a downwardly extending arc on said mounting means to lift the elevating platform, an intermediate link pivoted to said lifting wheel link and to said tension member and through the intermediary of which said tension member swings said lifting link downwardly, and means guiding the movement of said intermediate link so located that when said lifting wheel link is in its upward position and said platform is lowered, the pivot between said tension means and intermediate link will be vertically displaced below the pivot between said intermediate link and said lifting wheel link.

HERBERT J. FRAMI-IEIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Y 

